Wednesday, February 19, 2014

Quirks in the cladistic analysis of Lourinhasaurus

It's been barely a year since the second of the three Jurassic Portuguese sauropods, the brachiosaurid titanosauriform Lusotitan ataialensis, was put in a cladistic context by Mannion et. al. (2013). Now, Mocho et. al. (2014) have published a paper re-assessing the cladistic position of the third described Portuguese sauropod, Lourinhasaurus alenquerensis, following in the footsteps of Mannion et. al. (2012, 2013) in putting all of Portugal's sauropod taxa in a phylogenetic context.As we all know, Lourinhasaurus was originally assigned to Apatosaurus by Lapparent and Zbyszewski (1957) and later referred to Camarasaurus by McIntosh (1990). However, Dantas et. al. (1998) removed alenquerensis from Camarasaurus and assigned it to a new genus Lourinhasaurus. Because the original description of this taxon had a rather inadequate diagnosis, Upchurch et. al. (2004) found it to be in an unstable position in Eusauropoda.When browsing through the supplementary material for Mocho et. al. (2014), it's interesting that while the cladistic analyses both recover a monophyletic Camarasauridae formed by Camarasaurus, Lourinhasaurus, and Tehuelchesaurus, they treat nemegtosaurids as diplodocoids rather than titanosaurs and Haplocanthosaurus as a macronarian rather than a diplodocoid, while failing to support a monophyletic Euhelopodidae sensu D'Emic (2012). However, this is likely due to the failure of Mocho et. al. (2014) to incorporate characters from the cladistic analyses of D'Emic (2012) and Whitlock (2011).